Superheating arrangement for water-tube boilers



March J. N. D. HEENAN SUPERHEATING ARRANGEMENT FOR WATER TUBE BOILERS 1 Filed June 19, 1925 Patented Mar. 15,1927.

w rezrnr" JOHN nnrsoiv DUNDAQHEENAN, or..erinw cir,ronnon,.,nnsrai\in, assre-non ro POWER SPECIALTY COMPANY, OF

YORK;

'YORK, N. Y.., A. CORPORATION- OE. NEW

SUPERHEATING ARRANGEMENT FOR WATER-TUBE BOILERS.

Application filed June 19, 19%, Seria1 No. 38,145, and in Great Britain September 24, 1924.

The present invention relates to steam superheating arrangements in boiler furnaces adapted for the combustion of pulverized fuel.

Hitherto, it'has been found that when.

the boiler is of the water tube type and the superheater is located above the top bank of water tubes, the gas temperature is not sufficiently high to produce the requisite degree of superheat. If the superheater is mounted between the banks of tubes in a region where the gas temperature is appropriate, not only must the design of many boilers be modified but the superheater is relatively inaccessible for cleaning and other purposes. If the superheater is mounted in the gas path beneath the water tubes or in the combustion chamber proper the temperature is too high.

In order to overcome these disadvantages I arrange the superheater in the lower part of the combustion chamber beneath asocalled screen of water tubes serving to cool the molten slag as it falls into the ashpit.

Figures 1 and 2 of the accompanying drawings, illustrating two modes of carrying out this invention in practice, aresectional elevations, more or less diagrammatic, of the lower portions of typical combustion chambers of furnaces burning pulverized fuel. Pulverized fuel is injected downwardly at one side of the top of the combustion chamber and air, preferably preheated, is progressively admitted to support combustion. The products of combustion traverse a generally] U-shaped path in the combustion chamber, the ash or non-gaseous products being precipitated by gravity and inertia at the bottom of the path where the flow is indicated by arrows.

In accordance with known practice, a screen of water tubes 1 is disposed across the lower portion of the combustion chamber for the purpose of coolingthe precipitated molten ash and thereby preventing slagging on the floor of the combustion chamber and in the ashpit.

In Figure 1, the water tubes are doubleinclined as shown, 2 being the inlet header, 3 the outlet header and 4 the return header at the rear of the furnace. In Figure 2, the water tubes lie in the same inclined plane and the inlet and outlet headers 2 and 3 are located on oppositesides of the I I furnace.

The superheater tubes 5, which according to this invention are disposed beneath the screen of water tubes, are preferably in Figure 1, where the ashpit is at the front of the furnace, in the form of U-shaped tubes connected to inlet and outlet headers 6 and 7. The tubes 5 are mounted and supported with refractory packing in an opening in the wall of the combustion chamber, and

additional support, in the form of refractory blocks 8 for example, may be provided for the free ends of the tubes in the combustion chamber. 7

In Figure 2, where the ashpit is centrally disposed at the bottom of the combustion chamber, the superheater tubes 5 are. straight and connected by inlet and outlet headers 6 and 7 on opposite sides of the furnace. The superheater tubes are mounted and supported in a manner which will enable them to bereadily withdrawn for inspection and replacement. i I

lVith the superheating arrangements hereinbefore described and illustrated v in the drawings, the hot products of combustion are tempered before sweeping the super-' heater tubes to a degree which is generally appropriate for superheating purposes.

It will be understood that many modifications may be made in the-arrangement and B5 disposition of the superheater tubes beneath the screen of water tubes without departing outside the scope of this inventionas I herein set forth.

.I claim:

' 1. In a boiler furnace burning pulverized fuel and having a screenof water tubes in the path of the precipitated ash,- the provision'of a superheater interposed between the water tubes andthe ashpit, substantially I as andforthe purpose set forth. v

2. In a boiler furnace burning pulverized fuel the combination of a screen of water tubes across the lower part of the combustion chamber and a superheater located beneath the water tubes, substantially as and for the purpose set forth.

8. In a boiler furnace burning pulverized fuel and having a screen of water tubes in the path ofthe precipitated ash,'the provision of superheater tubes arrangedand dis- 2'- v v 1',e21,112

posed to be swept by the ash and other ber beneath the fuel inlet and heating gas products of combustion after the latter have. outlet from said chamber, theimprovement 10' been tempered by passage between the Water which consists in a superheater located imtube's. mediately beneath said screen in the path '5 7 4:. In a boiler furnace burning pulverized of the products of combustion passing fuel and having a combustion chamber and through said screen;

a screen of Water tubes extending across v v V the lower portion of the combustion cham- JOHN NELSON DUN DAS HEENAN. 

